1. Field of the Invention
The present invention relates to a modular ballistic wall for decelerating projectiles. More specifically, the present invention relates to a wall which may be used in shoot houses, baffles, and the like, for safely decelerating projectiles.
2. State of the Art
In order to maintain proficiency in the use of firearms, it is common for law enforcement officers and sportsmen to engage in target practice. While target practice has traditionally been conducted on a range in which targets were placed a distance away from the shooter, many have realized that such a scenario does not adequately train officers for many real life situations. For example, a substantial percentage of the police officers who are killed each year are killed within fifteen feet of the perpetrator. Many are killed within five feet—often within the confines of a house or other building.
In order to better train police officers, many began building ballistic walls in arrangements to resemble a house or other building. These structures, typically referred to as shoot houses, enabled police officers to train in situations in which the officer faces realistic threats to their safety.
Shoot houses were originally constructed out of a concrete, gravel filled walls, or tire walls. While these shoot houses provided marked improvement over traditional training, they still do not feel as realistic as conventional looking walls.
A significant improvement in shoot houses was achieved with the invention of modular shoot house walls in which plates of steel were attached together in a ballistically sound manner and then covered by a frame. The frame typically had two-by-fours attached to facing strips that held the plates together, and pieces of plywood that connected the two-by-fours. A more detailed description of a preferred construction of the shoot house is set forth in U.S. Pat. No. 5,822,936.
When the plywood was painted, the shoot house looked very similar to a conventional home with the roof removed. In such a shoot house, the officer is able to train in a ballistically safe environment that closely resembles what may be the most dangerous scenario that he will face.
While U.S. Pat. No. 5,822,936 teaches that a preferred embodiment of the invention avoids the necessity of cutting holes in the plate, some have insisted that the bolts which hold the facing and backing strips to the plates extend through the plates. This is due to an erroneous understanding perpetuated by some that the clamping of the facing and backing strips together against the plates leaves the wall prone to separation.
The disadvantage of cutting holes in the plates is that each time the cutting torch is turned off, there is an associated cost. In order to properly secure the plates and prevent bullet fragments from passing through joints in the wall, as many as eight attachment points should be used. Thus, even if the cost associated with turning off and on the torch is only $0.20, the cost associated with a single plate can be several dollars.
Thus, there is a need to form a modular ballistic wall which does not have the associated costs of repeatedly turning off the cutting torch, while providing the perceived benefit of the attachment bolts going through the plates.
Another problem which is present in some modular shoot houses is the method by which the two-by-fours are attached to the facing strips. In one currently marketed arrangement, the two-by-fours are drilled and the attachment bolts extend through the two-by-fours, the facing strip, the plates and the backing strip. Such an arrangement is fundamentally flawed. As bullets impact the two-by-four adjacent the bolts, the two-by-four will be damaged by each round. Over time the support given to the bolt by the two-by-four will decrease and the bolt will become loose. Once the bolt is able to move, the facing and backing strips are no longer held securely against the plate and the risk that a bullet or bullet fragment will pass through the seam between the plates increases significantly.
The risks associated with loose bolts can be avoided by making sure that a substantial number of the attachment bolts hold the facing and backing strips together without passing through the two-by-four. Such a situation, however, still raises the concern that the two-by-fours must be milled or otherwise handled so that the holes for the bolts can be drilled therein. This usually results in the wood being shipped to the job site from the same location as the metal plates, facing strip, etc. If drilling holes in the wood can be avoided, the wood can be purchased at a hardware store close to the site at which the range is being built. This can significantly decrease costs depending on the location of the shoot house.
Thus, there is needed an improved mechanism for attaching a wood or other containment frame to the facing strips. Ideally, such a mechanism would not use attachment bolts used to secure the facing strip and backing strip to the metal plates.